129Xe NMR spectroscopy

Hyperpolarized 129Xe NMR Spectroscopy, MRI and Dynamic NMR Microscopy for the In Situ Monitoring of Gas Dynamics in Opaque Media Including Combustion Processes 

A number of recent developments in 129Xe NMR spectroscopy are presented with direct applications to the study of mesopore space in solids. This includes the establishment of a relationship between pore size and chemical shifts for a number of controlled pore glasses and the exploration of hyperpolarized (HP) xenon for a number of NMR and microimaging applications to porous solids. With HP xenon, the increase in experimental sensitivity is remarkable. Experiments illustrated include the rapid characterization of the void space in porous solids, including the in-situ study of processes such as diffusion and dehydration, and imaging with chemical shift resolution. 

From Figure 12.3, it can be concluded that room temperature 129Xe NMR spectroscopy is especially well suited for the investigation of amorphous domains in polymer materials 

Hydrate structures containing hydrate former + Xe help gas have been confirmed by 129Xe NMR spectroscopy by Ripmeester and Ratcliffe (1990a). 

Several reviews on xenon NMR spectroscopy have appeared [1, 2], therefore in this introduction only the most important aspects will be discussed. The xenon atom has two isotopes which are suited for NMR studies, the 129Xe and 131Xe isotopes. For most studies 129Xe is more convenient than 131Xe, while the former nucleus with spin I=V2 does not have an electrical quadrupole moment. In some cases, however, the quadrupolar interaction can provide additional (spectral and relaxation) information. Flere we will only consider the 129Xe isotope. 

The nature of xenon adsorbed on a metal single crystal surface (Ir(l 11)) was studied by 129Xe NMR spectroscopy.669 2H and 129Xe NMR spectra were used to follow the sorption of CD4 or Xe by a flexible microporous polymer, catena-bis(dibenzoylmethanato)(4,4 -bipy)nickel(II).670 

The possible use of this material as a porous solid was later evaluated using hyperpolarized 129Xe NMR spectroscopy, which demonstrated the permanent porosity of the material even after the removal of the co-crystallized solvent [53]. 

Fig. 5.3.10 (A) Polarization obtained contin- lasers (squares). (B) Actual intensities as uous-flow hp-xenon experiment as a function of measured by 129Xe NMR spectroscopy at xenon partial pressure for two different laser 110.69 MHz using 29-W laser power (triangles) powers, i.e., one 30-W diode array laser (tri- and full laser power (squares). Adapted from angles) and two combined 30-W diode array Ref. [16].

---